长江中游的泥沙淤积问题

长江上游年产泥沙5.12×10⁸ t, 经宜昌输入中游, 长江中游干流及各支流年产沙约 0.80×10⁸ t. 这两部分中约1.24×10⁸ t沉积于中游河湖中, 4.68×10⁸ t经大通输入下游, 沉淤于河道及长江三角洲或入海. 长江中游的泥沙, 总体是淤大于冲, 但是冲淤的地理分布、时间段分布和河床断面分布不均衡. 长江干流的宜昌-城陵矶段、九江-大通段冲大于淤或冲淤平衡. 淤积主要发生在长江干流以武汉为中心的螺山-武汉-黄石段以及洞庭湖区和鄱阳湖区. 即使在主要淤积江段, 也有局部时段和江段以冲刷为主. 主泓所在的河槽以冲刷为主, 而河道两侧或河道之间的洲滩, 则以淤为主, 形成高而平的漫滩, 往往被人为改造成圩垸. 荆江以北的江汉平原因有大堤从长江隔开, 只有汉水少量泥沙供应, 冲淤量很小, 再加上构造沉降的累计效应, 其地面高程绝大部分低于干流洲滩数米. 螺山-武汉-黄石段的淤积导致该段及以上江段洪水位抬高. 干流断面冲槽淤滩使长江中游河道的典型形态呈深河谷、高漫滩, 靠干堤保护堤内平原. 这种断面在洪水时成为在同等水量下, 水位不断抬高的原因. 高水位要高堤防来防堵, 这就增加了堤防压力、水头压力, 容易导致管涌、渗漏等险情. 堤外滩及洪水位与构造沉降的堤内平原间的高差不断增大. 三峡工程建成后, 水库拦沙及中游河道冲深, 可使同流量下水位大幅度降低, 但城陵矶-武汉段冲刷量很小, 不能解决该段及以下江段的泥沙淤积问题, 因此江汉平原因相对于洪水位地势过低而造成的洪涝灾害及相关环境问题, 仍将是中游长远的重大隐患.     

末次冰期东海陆架平原上的长江古河道

根据高分辨率浅地层剖面探测资料, 划分出虎皮礁凸起东南部浙东-西湖凹陷区末次冰期古河道体系.古河道充填沉积体的分布表明, 在末次冰期低海面时期, 长江主要途经长江凹陷进入外部陆架低地平原, 由于平缓地形的缓冲作用, 流入冲绳海槽的大型古河道难以发育, 但对低海面时期冲绳海槽北部的淡化起到了重要作用. 进一步分析认为, 在长江口外有6条大型古河道系统(A~F), 是末次冰期长江在东海陆架平原上的主要流路, 古河道分布与现在海底带状高地形有对应关系.     

长江中游城市群水资源承载力时空格局及耦合协调性

长江中游城市群是实施生态优先绿色发展战略的重点区域,从水资源承载系统内的水资源、社会、经济、生态环境4个子系统中选取24项指标构建水资源承载力评价体系,综合运用改进熵权TOPSIS模型、空间自相关分析和耦合协调发展模型定量评价2012-2018年长江中游城市群水资源承载力时空变化过程及子系统间的耦合协调性.结果表明,（1）长江中游城市群整体水资源承载力水平表现为：缓慢上升（2012-2015年）、下降（2015-2017年）、再上升的趋势（2017-2018年）;（2）水资源承载力的空间差异不明显（仅2016年差异显著）,武汉城市圈水资源承载力的空间差异相对较大且呈现低值包围高值的空间分布特征;（3）各城市生态环境子系统承载力得分较为均衡,但其他子系统的承载力均差异较大;（4）影响水资源承载力的主要因素依次为城市污水处理厂日处理能力、人均GDP、城镇化率、第三产业比重和人均水资源量;（5）长江中游城市群水资源承载系统的耦合协调度总体处于中等水平,且水资源承载力与耦合协调度有极强的正相关关系.研究结果可为长江中游城市群水资源承载力改善及水资源优化配置提供依据.     

基于Copula的洞庭湖-流域-长江系统水文干旱概率分析

洞庭湖是长江中游重要的通江湖泊,水系格局复杂.近年来在气候变化和人类活动的双重影响下,江湖关系发生变化,湖泊水文干旱事件频发.基于洞庭湖、流域和长江干流水文站点的实测数据,通过标准化水位指数和标准化径流指数识别了水文干旱事件,并运用Copula函数分析了洞庭湖-流域-长江系统水文干旱的联合概率分布特征.结果表明:在年尺度上,1964—2016年间洞庭湖共发生了9次水文干旱事件,水文干旱的发生概率为14.01%,洞庭湖-流域系统、洞庭湖-长江系统的水文干旱联合概率分别为9.65%和8.58%,表明年尺度上流域来水对洞庭湖水文干旱的影响更大.在季节尺度上,洞庭湖-流域系统春季水文干旱联合概率最高,且两者同时发生水文干旱事件的次数最多,表明洞庭湖春季水文干旱与流域入湖补给减少有密切关系;而洞庭湖-长江系统,其秋季水文干旱联合概率最大,尤其自2003年以后更加极端和频发,这一方面受秋季降水减少和流域内人类活动的影响,另一方面三峡水库秋季蓄水使长江中下游干流水位降低,长江对湖泊顶托作用减弱也是重要原因之一.     

2008年汶川Ms8．0地震多断裂破裂的近地表同震滑移及滑移分解

为深入理解汶川地震破裂的构造运动机制,本文选取典型的观测点,利用多种地质地貌标志测绘分析得到了汶川Ms8.0地震发震断裂的近地表三维同震滑移矢量.结果显示,北川-映秀断裂上的白水河-高川破裂段北西盘沿88°方位角水平滑移2.58 m、垂直滑移3.70 m;安县-灌县断裂上的白鹿-汉旺破裂北西盘沿134°方位角水平滑移1.63 m,垂直滑移2.00 m;小鱼洞破裂带南西盘沿76°～79°方位角水平滑移2.15～2.71 m,垂直滑移1.36～1.51 m.平行的白水河-高川破裂段和白鹿-汉旺破裂段合计形成1.72 m右旋走滑和3.49 m垂直断裂带的NW向水平缩短,总滑移方向(106°)与断裂带整体走向(42°)呈64°夹角,整个龙门山推覆构造带处于斜向挤压的构造环境.结合震源过程反演成果的分析显示,斜滑的白水河-高川破裂段和逆冲型白鹿-汉旺破裂段可能是在汶川地震中最大的一次子事件过程以滑移分解的形式而同时破裂形成的,滑移分解作用使两条断裂以斜滑与逆冲组合的力学性质产生破裂而非相同件质的斜滑破裂.小鱼洞破裂以低角度斜滑为主,可能是安县-灌县断裂与北川-映秀断裂以滑移分解形式同时破裂的纽带.小鱼洞断裂是龙门山断裂带长期处于斜向挤压的构造环境的产物,不只是逆冲断裂系中的捩断层.     

典型东北冷涡个例的平流层-对流层交换过程数值模拟研究

利用中尺度模式WRF对发生于2010年6月19~23日的我国东北地区一次典型冷涡过程开展高垂直分辨率数值模拟研究.在模式结果再现此次东北冷涡基本特征的基础上,进一步用Wei公式考察该冷涡引起的平流层-对流层质量交换的时空分布特征.分析结果表明,此次冷涡过程所引起的穿越对流层顶的质量交换总效应表现为平流层向对流层的净输送.在冷涡形成前期,即大型槽脊发展阶段,已经存在活跃的交换.在冷涡活动的整个过程中,槽后和冷涡移动方向的后部主要表现为空气质量由平流层向对流层的输送,而在槽前和冷涡移动方向的前部主要表现为由对流层向平流层的输送.这种空间分布形态主要是由对流层顶变化项决定,但由于其引起的向上、向下交换量作用相抵消,因此它对净交换量的贡献很小,而对此次过程净交换的贡献起决定性作用的是水平运动项.冷涡活动区域平均的总交换通量随时间的变化特征表现为三段:(1)在冷涡形成前期,存在较强的平流层空气向对流层输送过程;(2)随着冷涡的形成发展,总通量表现为TST-STT-TST波动趋势;(3)冷涡发展后期,又表现为平流层空气向对流层输送.     

2015年4月25日尼泊尔地震波场传播及烈度初步模拟分析

2015年4月25日尼泊尔发生Mw7.9地震.本文采用三维曲线坐标网格有限差分方法,依据USGS给出的震源运动学反演结果和震源区域地形数据,模拟了尼泊尔地震波场传播过程,得到震源区域烈度分布模拟结果,与实际观测的地表峰值速度(PGV)大体吻合.结果表明:地震烈度的空间分布整体上受控于震源的单边破裂特征,高烈度区域主要分布在破裂传播方向上,即震源东半部.震源南侧到东南侧近场,由于受到震源和地形的双重影响,形成最大烈度分布区域,最大烈度约为IX.南侧平原受低速沉积层影响形成高烈度区域.震源西侧及盆地内烈度相对较低.     

攀西裂谷带轻稀土矿床与地幔过程的关系

在攀西裂谷带集中分布着牦牛坪、大陆槽及攀枝花等轻稀土矿床(点),它们与霓石石英正长岩-碳酸岩杂岩体密切相关.碳、氧同位素研究表明,杂岩体中的碳酸岩是典型的岩浆碳酸岩,它是地幔过程的产物.电子探针研究显示,杂岩体中的流体-熔融包裹体富含轻稀土元素,反映其原始岩浆富集轻稀土,它可以为区域的轻稀土矿化提供充足的物质来源.赋存于霓石石英正长岩-碳酸岩杂岩体的稀土矿化与杂岩体有关它们均是地幔过程的产物.稀有气体同位素研究也在一定程度上揭示了轻稀土矿化与地幔过程之间存在着成因联系.     

长江中游泥沙与洪水来源的网湖沉积记录

在长江中游湖北省东部网湖湖心的采取柱状沉积物,用²¹⁰Pb+¹³⁷Cs方法测定表层的沉积速率.制作连续切片,选取深度7烈-88lmm的层型沉积较完整的一段样品,用显微镜量测浅色层和暗色层的厚度,采用电子探针确定层的地球化学成份,并由此计算了纹层的主要矿物组成.认为纹层主要是由于在洪水季节长江带来的浅色泥沙与在枯水季节富水河带来的含暗色矿物泥沙交替沉积形成的.泥沙主要来源于夏季长江倒灌入湖的洪水,部分来自长江支流富水河;冬季枯水季节,泥沙基本来源于长江支流富水河.     

由地震活动参数分析安宁河-则木河断裂带的现今活动习性及地震危险性

利用区域台网地震资料, 分析了川西安宁河-则木河断裂带不同段落的现今活动习性，进而鉴别潜在大地震危险的断裂段. 文中由异常低b值的分布圈绘出凹凸体，发展和应用了由多个地震活动参数值的组合判定断裂分段活动习性的方法，尝试了利用凹凸体段的震级频度关系参数估计特征地震的平均复发间隔. 结果表明，该研究断裂带存在5个不同现今活动习性的段落. 其中，安宁河断裂的冕宁-西昌段属于高应力下的闭锁段，其核心部分为一较大尺度的凹凸体；则木河断裂的西昌-普格段则表现为低应力下的微弱活动状态. 重新定位的震源深度分布，显示出上述闭锁段和微弱活动段的断层面轮廓. 冕宁-西昌段是未来大地震的潜在危险段. 该段从最晚的1952年6.7级地震起算，至未来特征地震的平均复发间隔估值为55～67年, 未来地震的震级估值为7.0～7.5. 本研究也初步表明，同-断裂段的活动习性可随时间动态演变.      

洪泽湖和淮河入洪泽湖河口的形成与演化

根据历史文献资料和前人研究成果,对洪泽湖和淮河入洪泽湖河口及三角洲的形成与演化进行了探讨。结果表明,洪泽湖是明,清两代治黄,保运工程的产物和组成部分,现代洪泽湖主要形成于１７世纪的靳治水时期,其形成后百余年中湖水位变化总趋势是不断上升,同时具有大幅度的年内年龄变化。     

黄河下游南四湖地区黄河河道变迁的湖泊沉积响应

黄河下游地区湖泊演化多与黄河河道变迁密切相关,进行高分辨率的湖泊沉积环境的研究,可揭示历史时期黄河下游的河道变迁,本文以南四湖ＤＳ孔为例,探讨河道变迁的湖泊沉响应。     

FLUVIAL PROCESSES IN THE LOWER JINGJIANG RIVER：IMPACT OF THE THREE GORGES RESERVOIR IMPOUNDMENT

Sediment supply to the lower Jingjiang River will be subject to substantial reduction after the impoundment of the Three Gorges Reservoir, which could result in an excess of carrying capacity and serious bank erosions in the downstream alluvial channel, threatening the bank protection works and the safety of the Jingjiang Dyke. This paper presents a summary of research works concerning the fluvial processes in the lower Jingjiang River and the possible impact of the Three Gorges Reservoir impoundment on the variation of its channel pattern. Three different predictions have been put forward by researchers: 1) the Jingjiang River will evolve towards a more sinuous, meandering channel pattern, with extensive bank erosion taking place along the river; 2) the river channel will be straightened and broadened because no point bar can be formed due to reduced sediment supply while bank erosion develops in the concave bank, and 3) this river reach will maintain its present channel pattern without significant change, although the sinuosity may be slightly reduced, since: a) the Three Gorges Reservoir mainly intercept sediment particles with sizes larger than 0.025mm, and b) the complex interaction between the Yangtze River and the Dongting Lake helps to reduce the negative effect of channel erosion through certain self-adjusting mechanism in fluvial processes. Discrepancy between these predictions shows that further research efforts are needed to understand the impact of Three Gorges Reservoir operation on the downstream fluvial processes. Meanwhile, there is an urgent need to closely monitor future development in the fluvial processes of the Jingjiang River and its influence on the safety of the Jingjiang Dykes.     

Shrinking of Dongting Lake and its weakening connection with the Yangtze River:Analysis of the impact on flooding

In this article,the shrinking of Dongting Lake and its progressively weakening connection with the Yangtze River and their impact on flooding before and after the implementation of the Three Gorges Project are analyzed.In recent decades,human activity combined with natural processes has altered the flow of the middle reach channel of the Yangtze River and interfered with its connection with Dongting Lake.This has resulted in progressively more frequent flooding in the area.This study uses hydrological data to analyze the annual maximum discharge and annual maximum stage development of the middle reach of the Yangtze River and Dongting Lake.In recent decades before the Three Gorges Project became operational in 2003,the annual maximum discharge and the maximum stage recorded in the middle reach of the river downstream of Dongting Lake had increased,a result of the weakening of the flood regulation function of Dongting Lake;the annual maximum stage at Luoshan station(downstream,close to the confluence of the Yangtze River and Dongting Lake) had risen by about 2.0 m during 1955-2005,(1.5 m attributed to annual maximum discharge and 0.5 m to river channel deposition).Observational data recorded after the Three Gorges Project was put into operation in 2003,it can be seen that deposition in the Dongting Lake has nearly ceased and the lake's connection with the Yangtze River is stable.It is evident that the flood regulation function of Dongting Lake will continue,and that during the lifetime of the Three Gorges Project,the flood situation in the middle reach of the Yangtze River and Dongting Lake will remain stable.     

NUMERICAL SIMULATION OF FLOOD DETENTION OPERATION IN MULTIPLY CONNECTED RIVER CHANNEL NETWORK

IINTRODUCTIONAccuratepredictionoftheconsequencesofaflooddetelltion-diversionoperationincomplexriverchannelnetworkisofgreatimportancetothedecisionmakingprocess.InthisregardtWotypesofmodelavailableforsimulatingsuchoperationsarefarfromsatisfactory,duetotheintricatenatUreofprocessesinvolvedintheseoperations.Thefirstmodeltype,i.e.,thewidelyusedhydrologicalmodels,dependsonsystematicwaterstageanddischargemeasurementsatgaugestations,andtheirpredictionsarelimitedtovariationsimwaterstageanddischar…     

云梦泽与荆江三角洲的历史变迁

本文通过对大量地质地貌、考古和文史资料的综合考证与分析,讨论了(1)云梦泽的形成、范围与兴衰历史;(2)荆江三角洲变迁的过程、阶段与特征;(3)荆江三角洲与洪涝灾害;(4)江湖历史变迁与问题思考等。     

河网水质管理决策支持系统在引江济太中的应用

利用太湖流域河网水质管理决策支持系统（TAIHU DSS）,对2000年夏季望虞河应急调水进行了技术方案比较,论证,重点对望虞河引江应急调水过程中,常熟枢纽泵站运用,望虞河东岸分流与否及望虞河立交开闸前对底水的处理等不同条件下的望虞河入湖水量,水质等进行多方案比较,为望虞河启用泵站调水、东岸适当分流,先打开蠡河船闸处理望虞河底水的方案提供了决策的技术依据,并引发了对太湖流域引江济太工作的进一步深入研究和实践,是决策支持系统在实际工作中的成功应用之一。     

洞庭湖近几十年来湖盆变化及冲淤特征

洞庭湖是我国著名的五大淡水湖泊之一,位于长江中游荆江段南岸,湖南省境内.历史时期,曾经是我国第一大淡水湖,直至新中国成立初期,湖泊面积仍然有4350km2,居我国淡水湖泊之首位.但由于洞庭湖承纳“四水”,吞吐长江,长江大量水沙涌入洞庭湖,造成了湖盆迅速淤高,加之由此诱发的人类大规模地湖泊垦殖活动,湖泊急剧萎缩.目前,洞庭湖已退居鄱阳湖之后,为我国第二大淡水湖泊.湖泊的严重泥沙淤积,已经造成了湖泊调蓄长江中游洪水功能的严重衰退,不但危及湖南省的防洪的安全,而且危及长江中下游地区的防洪安全,研究洞庭湖的湖盆冲淤演变具有重要意义.本文根据1974、1988和1998年洞庭湖125000水下地形资料,并针对洞庭湖具有显著上下游水位落差的实际,分不同高程和不同水位情况下,分析洞庭湖湖泊面积和容积演变特征,探讨洞庭湖近几十年来的湖盆变化及冲淤规律,试图揭示洞庭湖湖泊调蓄能力的变化过程.     

Ice cover of the Amur River and its impact on channel processes

Special features of the Amur R. ice regime in its middle and lower reaches are discussed along with the role of river ice in bank erosion, transport of coarse fragmental material, bottom washout, and water flow redistribution among branches. Numerous and various consequences of the ice drift impact on the banks and floodplain, as well as the intensity of erosion processes in the Amur River channel during winter have been revealed. The water flow redistribution among the Amur River branches near Khabarovsk noticeably changed the ice regime, which was rehabilitated as a result of implementation of a complex of special measures.     

Channel morphologic processes of a highly sinuous bend approaching neck cutoff by bank erosion in the middle Yangtze River

The distal reach of the Lower Jingjiang River(LJR)in the middle of the Yangtze River consists of five adjacent bends,among which the Qigongling Bend is a U-shaped meander with a mean sinuosity of 2.2 and the narrowest neck 525 m in width.This bend is slowly approaching neck cutoff owing to progressive bank erosion.An abnormal phenomenon has occurred in this bend since the Three Gorges Reservoir(TGR)began to operate in 2003 which is erosion in the inner bank zone and deposition in the outer bank zone.This problem has not been fully understood because of the interplay of changes in water-sediment,bank erosion,and artificial bank revetment.In this study,aerial and remote sensing images,hydrological data,channel topography,and an existing bank erosion model are used to reveal channel morphodynamics of this bend and the trend of the potential neck cutoff induced by bank erosion.The study results show that the clear water released from the TGR has provided by forcefully eroded the point bar of inner bank but failed to scour the outer bank due to the protection of bank revetment since the 1990 s.Thus far,the outer bank zone near the bend apex has increasingly widened in conjunction with the formation of 2 emerging sand bars.Consequently,the thalweg of the main channel has laterally shifted toward the inner bank by roughly 800 m.More severely,the rate of bank retreat on the upstream side of the bend neck was about 4.5 m/yr in 2010-2019,but the downstream side of this neck was experienced slight deposition.Bank erosion could be accelerated by progressively increasing erosion and eventually trigger the occurrence of neck cutoff in the next few decades,thereby significantly altering the quasi-equilibrium regime of channel morphodynamics in the LJR.